CN111225802A

CN111225802A - Method for forming sheet-like substrate

Info

Publication number: CN111225802A
Application number: CN201880066557.1A
Authority: CN
Inventors: M·D·M·迪茨迪亚兹; N·哈伯兰; R·弗理延斯
Original assignee: Daetwyler Sealing Solutions International AG
Current assignee: Daetwyler Schweiz AG
Priority date: 2017-10-11
Filing date: 2018-09-25
Publication date: 2020-06-02
Anticipated expiration: 2038-09-25
Also published as: WO2019072544A1; EP3694726B1; CN111225802B; US20200307065A1; CH714230A2; EP3694726A1

Abstract

The invention relates to a method for forming a dimensionally stable three-dimensional shape on a sheet-like substrate (3) of thermoplastic material, comprising the steps of: (a) providing a mold comprising a first mold (1) having a first template surface (11) for contacting an upper surface (31) of the substrate (3) and a second mold (2) having a second template surface (21) for contacting a lower surface (32) of the substrate (3) opposite the upper surface (31) of the substrate (3); each template surface (11, 21) having the inverse of the desired shape to be transformed into an upper surface (31) and a lower surface (32) of the substrate (3); and at least one of the first mode (1) and the second mode (2) is transparent to electromagnetic waves of a predetermined wavelength; (b) providing at least one absorbing layer (5, 5 ') capable of being heated by absorption of electromagnetic radiation (4, 4') of a predetermined wavelength, thereby heating the thermoplastic substrate (3) to or above its glass transition temperature; (c) placing a substrate (3) between a first die (1) and a second die (2) of a mold and closing the mold; (d) the absorbing layer (5, 5 ') is irradiated with electromagnetic radiation (4, 4') so as to heat the thermoplastic substrate (3) to or above its glass transition temperature for a sufficient time to transform the thermoplastic substrate into a three-dimensional shape.

Description

Method for forming sheet-like substrate

Technical Field

The present invention relates to a method for forming a dimensionally stable three-dimensional shape on a sheet-like substrate of thermoplastic material.

Background

Thin plastic films with specific three-dimensional characteristics can be used, for example, as control diaphragms for diaphragm carburetors. Examples of such membranes are described in WO2016012233 or swiss patent application No. 00038/16. The membrane comprises a dimensionally stable three-dimensional shape in the form of a plurality of concentric corrugations.

Sheet-like substrates are typically processed by thermoforming manufacturing techniques, such as mechanical thermoforming using male and female molds or vacuum or pressure thermoforming. However, vacuum or pressure thermoforming is only suitable for cup-shaped structures and does not allow obtaining very fine and precise structures on both sides of the sheet. Finer structures can be obtained by mechanical thermoforming (e.g. matched mould forming or hot embossing). However, it is almost impossible to accurately form a two-dimensional flat sheet or film of plastic having a thickness of less than 100 microns into a dimensionally stable three-dimensional shape.

Furthermore, thermoforming or hot embossing with a matching mold is costly and has a long cycle time due to the long heating and cooling cycles of the mold, since the entire mold is preheated to the glass transition temperature of the thermoplastic material or higher during each cycle. This is particularly true for thermal processing of plastics with high glass transition temperatures.

Another problem with known thermoforming techniques is that they are not suitable for making membranes having structural features of different thicknesses, such as a thickened central portion that is several times thicker than the remaining area of the membrane.

Accordingly, there is a need for a fast and highly accurate manufacturing method to form dimensionally stable three-dimensional shapes on sheet-like substrates of thermoplastic materials.

Disclosure of Invention

It is an object of the present invention to provide a fast and highly accurate manufacturing method for forming dimensionally stable three-dimensional shapes on a sheet-like substrate of thermoplastic material.

This is achieved by a method according to claim 1 and an apparatus according to claim 9. A method for forming a dimensionally stable three-dimensional shape on a sheet-like substrate of thermoplastic material comprises the steps of: (a) providing a mold including a first mold (die) having a first template surface for contacting an upper surface of the sheet-like substrate and a second mold having a second template surface for contacting a lower surface of the sheet-like substrate opposite the upper surface of the sheet-like substrate; each template surface has an inverted (reverse) shape of the desired shape to be converted into the upper and lower surfaces of the substrate; and at least one of the first and second modes is transparent to electromagnetic waves of a predetermined wavelength; (b) providing at least one absorbing layer capable of being heated by absorption of electromagnetic radiation of a predetermined wavelength, thereby heating the thermoplastic substrate to or above its glass transition temperature; (c) placing the substrate between a first mold and a second mold of a mold and closing the mold; (d) the absorbing layer is irradiated with electromagnetic radiation to heat the thermoplastic substrate to or above its glass transition temperature for a sufficient time to transform the thermoplastic material into a three-dimensional shape.

The present method thus allows the formation of a flat sheet-like substrate into a non-flat product having a dimensionally stable shape, such as a film sheet as described in WO2016012233 or swiss patent application No. 00038/16. The sheet-form substrate may be a film, sheet or foil of thermoplastic material. The sheet-like substrate suitable for use in the present method may preferably have a thickness of between 5 microns and 5 mm, preferably between 8 microns and 500 microns. The thermoplastic material may be selected from the group consisting of: polybenzimidazole (PBI), Polyimide (PI), Thermoplastic Polyimide (TPI), Polyamideimide (PAI), Polyethersulfone (PES), polyphenylsulfone (PPSU), Polyetherimide (PEI), Polysulfone (PSU), Polyetherketone (PEK), Polyaryletherketone (PAEK), polyphenylene sulfide (PPS), perfluoroalkoxy Polymer (PFA), Ethylene Tetrafluoroethylene (ETFE), Polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polybutylene terephthalate (PBT), or Polyetheretherketone (PEEK).

The electromagnetic wave may be emitted from a pulsed source having a wavelength of 200nm to 2000 nm.

The absorbing layer may be a metal layer disposed over the first and/or second template surface. Typically, the thickness of the metal layer will be between tens of nanometers to hundreds of nanometers. The radiation source then emits a beam (beam) which passes through the first and/or second mode and is incident on the metal layer, which absorbs the beam and heats up rapidly. The portion of the absorbing layer in contact with the upper and/or lower surface of the sheet-like substrate transfers heat to the sheet-like substrate, the sheet-like substrate is raised to or above its glass transition temperature, and the sheet-like substrate is transformed to obtain a dimensionally stable three-dimensional shape.

Where more than one absorbing layer is provided, the absorbing layers may be of different materials that can be heated by the same or different wavelengths of radiation.

With the described method, a sheet-like substrate can be double-sided molded.

Preferred embodiments of the invention are set out in the dependent claims.

In some embodiments, at least one of the first template surface and the second template surface is provided with an absorbing layer. In the case where both template surfaces are provided with an absorbing layer, two radiation sources may be used to irradiate both layers through their respective transparent molds.

In some embodiments, the sheet-like substrate is provided with an absorbent layer. Such a layer may be coated on the sheet-like substrate, or may be the sheet-like substrate itself.

In some embodiments, the sheet substrate may be transparent to electromagnetic waves of a predetermined wavelength.

In some embodiments, the sheet substrate may comprise a material suitable for absorbing electromagnetic radiation of a predetermined wavelength so as to be heated to or above its glass transition temperature.

In some embodiments, the sheet-like substrate may comprise at least two portions, preferably two layers. During step d, the at least two parts may be melted together.

In some embodiments, the absorbent layer may be provided only to the area where the sheet-like substrate is to be melted.

In some embodiments, to facilitate demolding, prior to step c, the surface of the sheet-form substrate may be provided with a release coating. The release coating may be a hydrophobic coating. The coating may be a fluorinated coating, such as a fluorinated ethylene propylene coating. The coating may be in the range of 10 nm.

The invention also relates to a device for forming a dimensionally stable three-dimensional shape on a sheet-like substrate of thermoplastic material, the device comprising: (a) a mold including a first mold having a first template surface for contacting an upper surface of the sheet-like substrate and a second mold having a second template surface for contacting a lower surface of the sheet-like substrate opposite the upper surface of the sheet-like substrate; each template surface having an inverse of the desired shape to be converted into the upper and lower surfaces of the substrate; and at least one of the first mode and the second mode is transparent to electromagnetic waves of a predetermined wavelength; and, (b) a source of electromagnetic radiation of a predetermined wavelength to heat an absorption layer disposed between the first template surface and the second template surface.

The electromagnetic wave source may be a pulsed source having a wavelength of 200nm to 2000 nm.

In some embodiments, at least one of the first template surface and the second template surface may be provided with an absorbing layer.

In some embodiments, the absorbent layer may be a single layer. The absorbing layer may be a metal layer, a graphite layer or a heat absorbing (heat absorbing) paint layer.

Drawings

The invention will be described in more detail hereinafter with reference to an embodiment shown in the drawings. The figures show:

FIG. 1 is a schematic illustration of a method for forming a dimensionally stable three-dimensional shape on a sheet-form substrate of thermoplastic material;

FIG. 2 is a schematic view of the mold during irradiation from one side;

FIG. 3 is a schematic view of the mold during irradiation from both sides;

FIG. 4 is a schematic illustration of a method having an absorber layer disposed on a substrate;

FIG. 5 is a diaphragm that may be manufactured by the method of FIG. 1;

fig. 6 is a schematic illustration of a method for forming a dimensionally stable three-dimensional shape on a sheet-form substrate of thermoplastic material comprising a combination of two layers.

Detailed Description

Fig. 1 shows a schematic view of a method for forming a dimensionally stable three-dimensional shape on a sheet-like substrate 3 of thermoplastic material.

Fig. 1(a) shows an open mold having a first mold 1 having a first mold plate surface 11 and a second mold 2 having a second mold plate surface 21. The first template surface 11 has a shape that is the inverse of the desired three-dimensional structure to be formed into the upper surface 31 of the sheet substrate 3. The second template surface 21 has a shape that is the inverse of the desired three-dimensional structure to be formed into the lower surface 32 of the sheet substrate 3. As shown in fig. 1 and 2, the first template surface 11 and the second template surface 21 may have complementary shapes. However, non-complementary shapes are also possible, as long as the thermoplastic material is sufficiently displaceable (displaced) in its molten state, as shown in fig. 3 and 4.

The sheet-like substrate 3 may be a flat sheet, foil or film having a thickness in the range of 5 to 5000 micrometers (preferably 25 to 500 micrometers), and is placed between the first mold 1 and the second mold 2. With respect to the present invention, the sheet-like substrate is two-dimensional before the method is applied. The substrate then has a dimensionally stable three-dimensional shape, for example with complementary corrugations to obtain, for example, a membrane with substantially the same overall thickness (fig. 1(c)), or with non-complementary corrugations (fig. 3) to obtain, for example, a membrane with a varying thickness.

Currently, good results have been achieved with 25 micron Polyetheretherketone (PEEK) films. However, thicker films may also be used, as well as other materials, such as Polybenzimidazole (PBI), Polyimide (PI), Thermoplastic Polyimide (TPI), Polyamideimide (PAI), Polyethersulfone (PES), polyphenylsulfone (PPSU), Polyetherimide (PEI), Polysulfone (PSU), Polyetherketone (PEK), Polyaryletherketone (PAEK), polyphenylene sulfide (PPS), perfluoroalkoxy Polymer (PFA), Ethylene Tetrafluoroethylene (ETFE), Polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), or polybutylene terephthalate (PBT).

In the method shown in fig. 1, the first template surface 11 of the first mold 1 is provided with an absorbing layer 5. The absorption layer 5 can be rapidly heated within a few milliseconds by electromagnetic radiation 4 from a pulsed source with a wavelength in the range of 200nm to 2000 nm. For irradiating the absorption layer 5, the first mode 1 is a material transparent to the wavelength of the electromagnetic radiation 4.

After or during mold closing (fig. 1(b)), the absorbing layer 5 absorbs the radiation 4 and rapidly heats up in order to transfer energy to the thermoplastic sheet substrate 3. The substrate 3 is thereby heated until it is sufficiently hot, typically at or above its glass transition temperature, to be transformed into the desired three-dimensional shape. During this process, the first mold 1 and/or the second mold 2 of the mold hardly heats up, and the mold can be opened almost immediately after stopping the irradiation 4, and the sheet-like substrate 3' after the conversion can be removed (see fig. 1 (c)). The mold is then ready for the next cycle.

As an alternative to the embodiment shown in fig. 1, the second mould 2 and the sheet-like substrate 3 may be transparent to radiation. In this case, the radiation may pass through the second mode 2 and the substrate 3 to reach the absorption layer 5 disposed on the first mode 1, as shown in fig. 2.

In order to process thicker sheet-like substrates, the first template surface 11 and the second template surface 21 may each be provided with an absorbing layer 5, 5'. In this case, both the first mold 1 and the second mold 2 are transparent and the absorbing layers 5,5' are irradiated from opposite sides, as shown in fig. 3.

Fig. 4 shows a variant of this method, in which the sheet-like substrate 3 itself is provided on one or both sides with an absorbing layer 5 coated on the substrate, or the substrate is made of a radiation-absorbing thermoplastic material. The first mode 1 and/or the second mode 2 are transparent and radiation can be directed onto the substrate from one or both sides.

Fig. 5 shows an example of an article that can be manufactured using a method according to the invention. The article is a film 6 made of thermoplastic film material as described in WO 2016012233. The diaphragm 6 in the form of a disc comprises a plurality of concentric corrugations 61 and radial stiffening ribs 62. Such a three-dimensional structure can be obtained by the above-described method. Good results have been achieved, for example, with a planar 25 micron thick PEEK film in which a plurality of circular, concentric corrugations have been formed, such as shown in the membrane of fig. 5.

As shown in fig. 6, this method also allows two or more layers of

substrates

3, 3a to be bonded together. Fig. 6(a) shows the mold in an open state before the

substrates

3, 3a are transformed. Fig. 6(b) shows the mold in an open state after converting the substrate into a substrate 3' having a dimensionally stable three-dimensional shape. In order to obtain a membrane, for example, having a plurality of concentric corrugations and a central portion several times thicker than the corrugated membrane, the separate portion 3a of the substrate may be placed centrally on the sheet-like substrate 3, as shown in fig. 6(a), or in one of the two dies 1, 2. An example of such a membrane is described in swiss patent application No. 00038/16.

The separating section 3a may be constructed as an absorption layer 5a, or may be provided with an absorption layer 5a on either side. During irradiation of the one or more

absorbing layers

5, 5a, the two

substrate portions

3, 3a are heated above the glass transition temperature of the thermoplastic material and thereby permanently bond together to form a dimensionally stable three-dimensional shape on the sheet-like substrate 3, as shown in fig. 6 (b).

It is to be understood that the invention is not limited to the embodiments described above. Those skilled in the art will be able to deduce other variants that also belong to the subject of the invention, using the knowledge of the invention.

Reference numerals

1 first mold

11 first template surface

2 second die

21 second template surface

3 sheet-like substrate

Part of a 3a sheet-like substrate

3' converted sheet substrate

31 upper surface of the container

32 lower surface

4,4' electromagnetic radiation

5,5' absorbing layer

5a absorbing layer

6 diaphragm

61 Concentric corrugations

62 radial rib

Claims

1. A method for forming a dimensionally stable three-dimensional shape on a sheet-like substrate (3) of thermoplastic material, comprising the steps of:

a. providing a mold comprising a first mold (1) having a first template surface (11) for contacting an upper surface (31) of the substrate (3) and a second mold (2) having a second template surface (21) for contacting a lower surface (32) of the substrate (3) opposite the upper surface (31) of the substrate (3); each template surface (11, 21) having the inverse of the desired shape to be transformed into the upper surface (31) and the lower surface (32) of the substrate (3); and at least one of said first mode (1) and said second mode (2) is transparent to electromagnetic waves of a predetermined wavelength;

b. providing at least one absorbing layer (5, 5 ') capable of being heated by absorption of electromagnetic radiation (4, 4') of a predetermined wavelength, thereby heating the thermoplastic substrate (3) to or above its glass transition temperature;

c. -placing the substrate (3) between the first (1) and the second (2) mould of the mould and closing the mould;

d. irradiating said absorbing layer (5, 5 ') with said electromagnetic radiation (4, 4') so as to heat said thermoplastic substrate (3) to or above its glass transition temperature for a sufficient time to transform said thermoplastic substrate into said three-dimensional shape.

2. The method according to claim 1, wherein at least one of the first template surface (11) and the second template surface (21) is provided with the absorbing layer (5, 5').

3. Method according to one of the preceding claims, wherein the sheet-like substrate (3, 3a) is provided with the absorption layer (5, 5').

4. The method according to one of the preceding claims, wherein the sheet-like substrate (3) comprises a material suitable for absorbing the electromagnetic radiation (4, 4') of a predetermined wavelength and forms the absorption layer (5, 5a) so as to be heated to or above its glass transition temperature.

5. Method according to one of the preceding claims, wherein the sheet-like substrate comprises at least two portions (3, 3a), preferably two layers.

6. Method according to claim 6, wherein during said step d said at least two portions (3, 3a) are melted together.

7. Method according to one of the preceding claims, wherein the absorption layer (5, 5', 5a) is provided only in the areas where the sheet-like substrate is to be melted.

8. Method according to one of the preceding claims, wherein, prior to step c, the surface of the sheet-like substrate (3) is provided with a hydrophobic coating.

9. An apparatus for forming a dimensionally stable three-dimensional shape on a sheet-like substrate (3) of thermoplastic material, the apparatus comprising:

-a mold comprising a first mold (1) having a first template surface (11) for contacting an upper surface (31) of the substrate (3) and a second mold (2) having a second template surface (21) for contacting a lower surface (32) of the substrate (3) opposite to the upper surface (31) of the substrate (3); each template surface (11, 21) having the inverse of the desired shape to be transformed into the upper surface (31) and the lower surface (32) of the substrate (3); and at least one of the first mode (1) and the second mode (2) is transparent to electromagnetic waves (4, 4') of a predetermined wavelength; and

-a source of electromagnetic radiation of a predetermined wavelength to heat an absorption layer (5, 5') arranged between the first template surface (11) and the second template surface (21).

10. The device according to claim 9, wherein at least one of the first template surface (11) and the second template surface (21) is provided with the absorbing layer (5, 5').

11. The device according to claim 9 or 10, wherein the absorbing layer (5, 5') is a metal layer, a graphite layer or a heat absorbing coating layer.